Subject: Pacific-NW: Subj/prognostic Reasoning For Tropical Depression 17w (seventeen)

From: SIU Weather Processor <[email-masked]>
Date: Fri, 22 Oct 2010 09:30:05 -0500

WDPN33 PGTW 220300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN)
WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TROPICAL DEPRESSION (TD) 17W (SEVENTEEN), LOCATED
APPROXIMATELY 620 NM NORTHEAST OF SAIPAN, HAS TRACKED NORTHWESTWARD
AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE
IMAGERY AND A 221136Z TRMM MICROWAVE PASS DEPICT TIGHTLY CURVED LOW
LEVEL BANDING WRAPPING INTO THE SYSTEM CENTER WITH A MAJORITY OF THE
DEEP CONVECTION BEING SHEARED TO THE SOUTHWEST. THERE IS FAIR
CONFIDENCE IN THE CURRENT POSITION BASED ON THE AFOREMENTIONED TRMM
PASS. THE CURRENT INTENSITY ESTIMATE OF 30 KNOTS IS CONSISTENT WITH
DVORAK ESTIMATES FROM PGTW AND KNES AT 221130Z AS WELL AS A 221132Z
ASCAT PASS INDICATING 25 TO 30 KNOT WINDS. UPPER LEVEL ANALYSIS
INDICATES TD 17W IS IN A MARGINAL ENVIRONMENT FOR FURTHER
DEVELOPMENT, WITH STRONG DIFFLUENCE ALOFT AND MODERATE NORTHEASTERLY
VERTICAL WIND SHEAR. TD 15W IS CURRENTLY TRACKING NORTHWESTWARD
UNDER THE INFLUENCE OF A LOW TO MID-LEVEL SUBTROPICAL STEERING RIDGE.
3. FORECAST REASONING.
    A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST REASONING
SINCE THE PREVIOUS BULLETIN.
    B. TD 17W IS FORECAST TO BEGIN TURNING POLEWARD WITHIN THE NEXT
12 HOURS AS THE SUBTROPICAL STEERING RIDGE IS WEAKENED BY A
TRANSITORY MID-LATITUDE TROUGH. AFTER TAU 12, THE SYSTEM IS EXPECTED
TO TRACK NORTHEASTWARD AHEAD OF A DIGGING MID-LEVEL TROUGH AND
WEAKEN TO BELOW WARNING CRITERIA BY TAU 36. THE AVAILABLE NUMERICAL
MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF WBAR WHICH
LOOPS THE SYSTEM TO THE SOUTH, INDICATIVE OF A WEAK STEERING
ENVIRONMENT. THIS FORECAST IS SLIGHTLY NORTH OF CONSENSUS AND FAVORS
A SLOWER POLEWARD TURN AHEAD OF THE TROUGH.//

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.